Ever wondered why some feel exhausted while others seem refreshed after just a few hours of sleep. The answer could be in your genes, says a new study.
Scientists claim to have found a "sleepiness" gene that affects whether people rise refreshed and ready to attack the day -- or would rather turn over and go back to sleep, the Daily Mail reported.
According to them, people with the "sleepiness" gene feel more tired than others, even after getting a good 10 hours of shut-eye two nights in a row; they also take lack of sleep harder than others.
For the study, the scientists focused on 37 volunteers who had a genetic flaw linked to narcolepsy, a sleep disorder in which sufferers fall asleep without warning. Despite having the gene, the men and women did not suffer from nacrolepsy and were classed as healthy sleepers.
For the first two nights of the study, they were allowed to sleep for up to 10 hours. For the next five, they were only allowed four hours in bed. Another 92 adults without the genetic flaw followed the same routine.
Those with the flawed gene were sleepier and more fatigued no matter how much or how little sleep they had. They also woke up more during the night and spent less time in restorative deep sleep, the findings revealed.